intf: movieHash: manage file opening errors properly

When failing to open a file to resolve the hash, the interface was
exiting on error because of the assertion. It can happen for a
number of reasons that the file cannot be opened and this should
not prevent TraktForVLC from working properly. This commit aims
at managing the error properly by showing an error message and
aborting the hash resolution.

Relates to #115

Signed-off-by: Raphaël Beamonte <[email protected]>

trakt.lua

@@ -310,7 +310,12 @@ end
 ------------------------------------------------------------------------------
 local
 function movieHash(fileName)
-    local fil = assert(io.open(fileName, 'rb'))
+    local fil, err = io.open(fileName, 'rb')
+    if not fil then
+        vlc.msg.err('Error opening file \'' .. fileName .. '\': ' ..
+                    err .. '; media hash will not be resolved.')
+        return
+    end
     local lo, hi = 0, 0
     for i = 1, 8192 do
         local a, b, c, d = fil:read(4):byte(1, 4)
@@ -1912,12 +1917,14 @@ function get_current_info()
         loc_cache_changed = true
     end
 
+    local media_hash, media_size
     if cache[infos['key']].uri_proto == 'file' and
             (not cache[infos['key']].hash or
              not cache[infos['key']].size) then
         -- Compute the media hash and size
-        local media_hash, media_size = movieHash(cache[infos['key']].uri_path)
-
+        media_hash, media_size = movieHash(cache[infos['key']].uri_path)
+    end
+    if media_hash then
         -- Check if any file in the cache matches those information
         for k,v in pairs(cache) do
             if v.hash == media_hash or v.size == media_size then